Computational investigation on effects of geo-mining parameters on layering and dispersion of methane in underground coal mines- A case study of Moonidih Colliery

Abstract

Managing methane and preventing methane layering is of paramount significance for safety in gassy underground coal mines. Methane layering behaviour and dispersion of methane in underground coal mines are influenced by several geo-mining parameters. In this paper, we investigate the effects of five important geo-mining parameters, such as air velocity, methane emission rate, width, surface roughness and inclination of mine gallery on methane layering and dispersion of methane in tailgate of a retreating longwall mine. The main objectives are to examine the effects of these parameters on variation of methane concentration and identify the critical parameters significantly affecting methane dispersion to a safer level in hard coal underground mines. Three-dimensional CFD simulations were performed using standard k-ε turbulence model taking into account the actual mine geometry and methane emission data of a gassy underground coal mine of India. The study revealed that air velocity plays a vital role on turbulent dispersion of methane and breaking methane layering in underground coal mines. Air velocity of 3.0 m/s was found adequate for dispersing methane to a safer level in the tailgate with 7.26 m3/min methane emission rate. Methane dispersion in the tailgate decreased with increase in methane emission rate and gallery width at a particular airflow rate. Increase in surface roughness and inclination of mine galley eased methane dispersion, nevertheless, their effects on methane dispersion found negligible.